Toyota Jidosha Kabushiki Kaisha

Kabushiki Toyota Chuo Kenkyusho

Atushi Ota

Yasuyuki Arakawa

Tamotsu Hasegawa

Minoru Uozumi

Hiroshi Kawahara

Yoshihiro Shimizu

Yoji Awano

Hirokazu Oonishi

In a vacuum casting method, a molding cavity is reduced in pressure to a vacuum, and when a gate is opened, a molten metal which has been raised to a molten metal retaining dome is charged into the molding cavity at a high speed. When a portion of a molten metal held in a molten metal holding furnace is raised to the molten metal retaining dome via a stalk, (1) the rising speed of a portion of the molten metal is set at 5-10 cm/sec, or (2) the rising speed is varied between an early stage of the rising motion and a later stage of the rising motion. In the latter method, the rising speed at the early stage of the rising motion is set at a speed higher than 10 cm/sec, while the rising speed at the later stage of the rising motion is set at 5-10 cm/sec. Due to the rising speed control, air involvement by the rising molten metal is effectively prevented.

Vacuum casting method

A vacuum casting apparatus in which a molding cavity is reduced in pressure substantially to a vacuum, and upon opening a gate, a molten metal which has been raised to a molten metal retaining dome is charged into the molding cavity via a runner at a high speed. The runner has a first portion making a pool of molten metal, a second portion connecting the molten metal retaining dome to the first portion, and a third portion connecting the first portion to the molding cavity. A pin is slidably provided in the first portion of the runner. An opening of the second portion of the runner to the first portion is located nearer to the pin than an opening of the third portion of the runner to the first portion. When the pin is moved into the first portion of the runner, the pin first closes the opening of the second portion and then begins to apply pressure the molten metal in the molding cavity.

Vacuum casting apparatus

In a method of vacuum casting wherein when the molten metal previously introduced into a molten metal reservoir is fed into a cavity, the lowest head of the molten metal in the molten metal reservoir is held to be higher than the level of a sprue, so that the cycle time of casting may be shortened and the quality of cast products may be improved. To this end, the interior of the molten metal reservoir is held gas tight while the sprue is opened by a gate member of straight tubular shape.

Method of and apparatus for vacuum casting

A vacuum casting apparatus includes a plurality of pressure pins arranged in a molding cavity, and at least one pressure pin is located in a portion of the molding cavity farthest from a gate. The pressure pins are operated to pressurize the molding cavity in an order from the pressure pin located farthest from the gate to a pressure pin located nearest to the gate. A cross-sectional area reduced portion can also be formed in a portion of a runner connecting the molding cavity and the molten metal retaining dome. A molten metal in the molding cavity is thereby suppressed from flowing backward into the molten metal retaining dome when being pressurized by the pressure pins, so that the quality of the cast products is improved.

Vacuum casting apparatus and method

Disclosed are an aluminum alloy casting having a high strength and a high toughness, and a production process for the same. The aluminum alloy casting comprises silicon (Si) in an amount of 2.5 to 4.4% by weight, copper (Cu) in an amount of 1.5 to 2.5% by weight, magnesium (Mg) in an amount of 0.2 to 0.5% by weight and the balance of aluminum (Al), and a matrix thereof includes a dendrite which has a size of 30 micrometers or less. Since the Si addition amount is suppressed as less as possible and since the size of the dendrite is micro-fined in the aluminum alloy casting, the toughness is improved remarkably. Further, since the Cu and Mg are added in the predetermined addition amounts, the strength is enhanced in the aluminum alloy casting. In addition, a solution treatment which is employed in the production process can further enhance the strength of the aluminum alloy casting.

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Toyota, Japan

Atushi Ota